Stabilization of an Induction Motor Drive – Part I: Modeling and Analysis”, submitted to

Abstract – Efficient torque control in combination with resonant DC-link input filters can cause stability problems for induction motor drives. The objectives of this paper and its companion are to design and analyze controllers to solve such problems. It is important to carefully choose the controller in order to improve stability while still having acceptable torque control and disturbance rejection. The key result is a unified framework for model based design of stabilization controllers. It covers both field-oriented control and direct torque control of motor drives. The focus of this paper (Part I) is on modeling and analysis. A linearized feedback model of the drive is derived and the stabilization problem is then interpreted as a standard loop-shaping problem, where the inverter input admittance should satisfy certain constraints. For large stability margins, the admittance should be positive real, at least around the resonance frequency of the input filter. To also guarantee good disturbance rejection, the magnitude of the admittance should be small for all frequencies. The companion paper (Part II) is devoted to synthesis and experiments, where stabilization controllers are designed to give the admittance the desired properties. Here, we also propose a simplified stabilization controller, which is easy to implement, while still providing a good compromise between damping and acceptable torque control. In Part II, the design is evaluated on a hardware-in-the-loop simulator. I